1. Field of the Invention
The present invention relates to a fuel supply device for an internal combustion engine, in which injectors are disposed at a downstream side and an upstream side of a throttle valve, respectively.
2. Related Art
With respect to a 4-cycle engine provided in a motorcycle or the like, there is a fuel supply device or apparatus that uses two injectors per one cylinder.
A fuel supply device, for an internal combustion engine, that includes a main injector at the downstream side of a throttle valve provided to a throttle body and an auxiliary injector at the upstream side of the throttle valve so as to supply fuel to both of the injectors from a fuel supply piping, is known from, for example, Patent Document 1 (Japanese Patent Laid-Open Publication No. 2005-188386).
The disclosed technology provides a fuel supply device for an internal combustion engine including a header pipe branched from the fuel supply piping in an airbox, and a bracket used for attaching each header pipe and a support member of a support plate are provided in the airbox.
Furthermore, Patent Document 1 discloses an example, in which the fuel supply device for an internal combustion engine, where the fuel supply piping is located outside the airbox and a fuel supply piping for the auxiliary injector is arranged outside the airbox.
In an arrangement of the fuel supply device for an internal combustion engine described in Patent Document 1, when the auxiliary injector and the fuel supply piping are arranged inside the airbox, since a bracket for fixing the fuel piping (a header pipe) and support members for a support plate and the like are provided, there are many support structures in the airbox. Accordingly, there causes a case in which the flow of intake air is disturbed and a pressure drop is caused, making smooth air supply difficult, or the box capacity is reduced due to the many support structures in the airbox.
Furthermore, in the case of arranging the fuel supply piping for the auxiliary injector outside the airbox, there also causes a case in which, for example, since the box capacity is sacrificed or reduced due to the installation outside the airbox, the intake air is easily influenced by the pulsation, and when the amount of intake air is drastically increased, the flow of the intake air is disturbed and the response is delayed.
Furthermore, if the auxiliary injector and a support structure supporting the fuel supply piping (the header pipe), the inside of the airbox is complicated, resulting in the increase of weight. Even if the inside of the airbox is complicated, the structure does not contribute to the reinforcement of the airbox, and there causes a problem in which, for example, a pressure drop is caused due to the flow of intake air being disturbed or that intake air resistance is increased.